Neurons affect each other at chemical synapses by the secretion of a neurotransmitter compound from one cell which exerts an excitatory or inhibitory influence on the next cell. Our knowledge about these junctions between cells, including the identity of transmitters and the mechanisms controlling the specificity of synaptic contacts, is basic to our understanding of the nervous system. The interesting physiology and anatomy of the lobster stomatogastric ganglion, and the muscles it innervates, make it an attractive system for the analysis of synaptic biochemistry. The objectives of this research are (1) to determine the neurotransmitter released by each of the 30 cells in the ganglion, and by the nerve endings which enter the ganglion from the CNS, and (2) to develop in vitro culture conditions for the ganglion which will allow a controlled analysis of the factors governing the regeneration of axons and the specificity of synapse formation. A sensitive radiochemical technique will be used to detect transmitter synthesis in individual cells and axons. The enzymes of transmitter synthesis will also be assayed in single cells. Extracts of growth-promoting and other neurosecretory structures will be examined for their influence on axon regeneration and synapse formation.